July is traditionally the year’s worst time for the unemployment rate, and last month was no exception.

San Diego County’s jobless rate jumped to 7.8 percent in July, as the region lost a net 10,900 nonfarm payroll jobs.

The state Employment Development Department reported Friday that the county’s unemployment rate rose from a revised 7.4 percent in June and 6.8 percent in May, which was the lowest since October 2008. The biggest job cut in July came from local government education, which reduced its workers by 11,500, mostly service employees for the summer break.

The data are not adjusted for seasonal factors, so the summer school-related reduction has a larger effect on the overall jobless figures. The job market is further squeezed in July by the influx of college graduates and high school students looking for work.

“There’s a lot of seasonality involved because the unemployment rate did surge,” said Alan Gin, economist at the University of San Diego.

But seasonality alone can’t account for an overall slowdown in the local job market. Between July 2012 and July 2013, county employers added a net 19,900 people to their payrolls, a growth rate of 1.6 percent. Consider that from July 2011 to July 2012, employers added 35,100 workers, which was a 2.9 percent clip. Annual growth is not affected by seasonality since it encompasses all times of the year.

“It’s disappointing,” Gin said, noting a solid annual number is around 25,000 new jobs. “It shows that the job growth is slowing. It could be that last year we were just rebounding off of such a terrible number in 2011 that you’re going to get good year-over-year comparisons.”

But as recently as March, jobs were growing annually at a 2.6 percent rate, with 32,600 workers added over that 12-month period. The most recent job growth numbers are not strong enough to keep up the pace.

There are a few economic headwinds that are slowing San Diego, economists say. The biggest is the sequestration, or $1.2 trillion in across-the-board federal spending cuts over 10 years that began in March. They specifically are hitting San Diego’s defense and research-laden economy. In July, more than 25,000 civilian Department of Defense employees took a 20 percent paycut, via weekly furloughs. The unpaid days off ended for most people this month, but could pick up again when the next federal fiscal year begins in October.

Another came at the beginning of the year, when the payroll tax holiday ended, Gin said. In January, the Social Security tax rate went back to 6.2 percent after two years at 4.2 percent to spur economic growth. That takes money out of wallets, as evidenced by recent disappointing earnings by Wal-Mart.

“San Diego’s economy continues to move forward but at a measured pace,” said Lynn Reaser, chief economist at Point Loma Nazarene University. “Businesses remain cautious in the face of defense budget cuts, rising health care costs, higher interest rates, and general uncertainty about the economy’s future.”